Shape memory materials have been used in packers to isolate portions of a wellbore as illustrated in U.S. Pat. Nos. 7,743,825 and 7,735,567. In these patents a packer made of a shape memory polymer (SMP) was delivered to a subterranean location and a heat input was applied using well fluids or a heater and an auxiliary compressive force applied to the packer element when it was made softer by the application of heat. The outside compressive force continued to be applied as the set position was achieved and the heat source was removed. The SMP then grew more rigid as it cooled with the mechanical force applied and the packer was ready for service. The sealing force in those references derived from the mechanical compression under heating conditions rather than any inherent shape memory features of the material. However, the methods described in these patents may require additional heating sources or a heating element to raise the temperature above the material's soft point or transition temperature. Therefore, it is desirable to have a material that can change shape from one to another by itself at downhole conditions to create sealing. The material can be run in hole in a small diameter, and activated to expand to larger diameter to fill space between a mandrel and a surrounding borehole. The material should preferably also be strong to maintain boost loads for sealing.
Relevant art to the present invention includes U.S. Pat. Nos. 6,976,537; 6,907,937; 6,907,936; 6,854,522; 6,446,717; 5,803,172; 4,475,847; 4,415,269; 4,191,254; 4,137,970 and 3,782,458 and U.S. patent applications: 2006/0124304 and 2005/0205263 as well as PCT references: WO 05059304; WO 05052316 and WO 03014517.
The present invention takes advantage of the shape memory feature of the material by making the material initially to the desired set dimension when the packer is placed at the desired subterranean location. Thus the ultimate set dimension is the dimension to which the packer element is initially produced. Before deployment the packer material is stretched when heated with a dummy or the actual mandrel placed inside. The material is stretched to reduce the outside dimension as much as possible without failure in a manner that keeps the inside diameter constant because the mandrel is in position. The material is cooled while retaining the stretching force so that a run in shape is developed. The run in shape has a lower profile for running in and the shape that the element will revert when heated downhole is the original manufactured shape. Regaining the original shape puts the element into contact with the surrounding wellbore wall. The seal made by such contact can be enhanced by an applied mechanical force. Those skilled in the art will better appreciate the full scope of the invention from a description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims.